eWON General Reference Guide - eWON wiki

5.11 MEM IO Server
5.11.1 Introduction
General Reference Guide IO Servers Configuration
The MEMORY IO Server is not a real IO server because values do not come from a peripheral. Memory Tags (Tags defined with the MEM IO
server) are rather sorts of variables that can be modified by a user input or by a BASIC application. These Tags are very useful for combining
different Tags and consider the result as an actual Tag i.e. having data logging capabilities and alarm management capabilities like for all other
Tags.
5.11.2 Setup
There is no setup for the MEM eWON IO server.
5.11.3 Tag name convention
IO Server Name MEM
Topic Name
RET
Item Name DON’T CARE
IO Server configuration
If no topic is specified, the Tag is a standard memory Tag. Its value is set to 0
when the eWON boots and the Tag is read/write, it can be updated through
user actions with script or web pages
If topic is set to RET, the Tag is retentive, each change is saved to flash and
when the eWON boots, the last value of the Tag is restored. This feature can
be convenient to use Tags as parameters.
The MEM "Item Name" is insignificant, the TagName is automatically copied
in the MEM address by the eWON, the user can change it, but the value will
immediately be overwritten again by the TagName.
Data type “Automatic” is equivalent to Floating Point.
Table 108: MEM IO server Tag name convention
Important: RET values are saved in the FLASH memory, this is not an immediate operation and the FLASH memory can only be
written and erased a limited (even if huge 100.000) number of times. This means that you should not use a BASIC script for
changing retentive values at very high rate. 1 Tag/Sec. is a maximum AVERAGE rate (occasional higher rates are not prohibited at
all).
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